Gas cylinder, in particular high-pressure gas cylinder

ABSTRACT

The invention relates to a gas cylinder, in particular a high-pressure gas cylinder, the cylinder tube ( 1 ) of which has a piston rod ( 9 ) that is passed through a sealing arrangement ( 13 ) by which the gas pressure prevailing in the pressure chamber ( 23 ) of the cylinder tube ( 1 ) is sealed off against the ambient pressure. The invention is characterised in that the scaling arrangement ( 13 ) has a compressed oil chamber ( 33 ) between at least one sealing element ( 31 ) adjacent to the pressure chamber ( 23 ) and at least one more sealing element further away from the pressure chamber ( 23 ), into which oil chamber oil can be pressed in by means of a supply device ( 51 ) at a pressure that is equal to or higher than the respective gas pressure prevailing in the pressure chamber ( 23 ) of the cylinder tube ( 1 ).

The invention relates to a gas cylinder, in particular a high-pressure gas cylinder, the cylinder tube of which has a piston rod that is passed through a sealing arrangement, which seals the gas pressure prevailing in the pressure chamber of the cylinder tube against the ambient pressure.

Such gas cylinders, as a kind of plunger cylinder, can be advantageously used as an energy storage cylinder in devices for energy recovery, among other things. As is disclosed by way of example in DE 10 2008 034 582 A1, in such applications, the piston rod of the gas cylinder is connected to a movable element of an associated work tool. The movable element may be the boom of an excavator or of a machine for material handling or the like, for example. When lowering the movable element, the potential energy of the movable element and the load connected thereto is stored by means of the gas cylinder, in order to provide at least partial compensation for the respective equipment weight when the movable element is raised again.

In the case of the higher pressures prevailing in the pressure chamber during operation, sealing the gas pressure against the ambient air is very difficult, even in the case of a working gas having relatively large molecules such as N2. It is scarcely possible to prevent gas losses with conventional sealing systems.

In view of this problem, the object of the invention is to provide a gas cylinder that offers increased security against gas losses.

According to the invention, this object is achieved by a gas cylinder having the features of claim 1 in its entirety.

Accordingly, an essential feature of the invention is that the sealing arrangement has multiple sealing elements, which are operationally subordinate to one another, wherein an oil pressure chamber is formed between a sealing element located closer to the pressure chamber and a sealing element located further from the pressure chamber, into which oil pressure chamber oil can be compressed by means of a supply device at a pressure that is equal to or higher than the respective gas pressure prevailing in the pressure chamber of the cylinder tube. The sealing element adjacent to the pressure chamber thus does not seal the working gas against the ambient air, but rather against the oil that is at the same pressure level, while the high-pressure oil that is located in the oil pressure chamber is sealed against the environment by means of the additional sealing element. Thus the sealing objective is divided into two manageable subtasks so that the greatest possible security against gas losses is achieved.

In an especially preferred embodiment of the gas cylinder arrangement according to the invention, the piston rod has a sliding element that can be moved in the cylinder tube, so that the piston rod is securely guided and supported at two opposing end regions within the cylinder tube. In this way, unimpeded operation is made possible.

In especially advantageous embodiments, the configuration is such that the sealing elements of the sealing arrangement and the oil pressure chamber located therebetween are disposed in a fixed positional relationship to one another. This makes it possible to realize the sealing arrangement in its entirety in a uniform component that forms an integral part of the cylinder tube.

It is especially advantageous that the supply device for the oil pressure chamber have a hydraulic accumulator, the oil side of which, which contains sealing oil, can be connected to the pressurized oil chamber and the gas side of which can be connected to the pressure chamber of the cylinder tube. The gas pressure in the pressure chamber is thereby utilized in an advantageous manner for the pressure supply of the foil pressure chamber, which leads to an especially simple and reliable structure of the supply device.

In advantageous embodiments, the supply device has an oil connection, by means of which the sealing oil can be refilled to the oil side of the hydraulic accumulator, wherein a device is preferably available for monitoring the quantity of sealing oil during operation. In this regard, at least one pressure sensor may be provided, which signals the oil pressure prevailing in the oil pressure chamber of the sealing arrangement.

The hydraulic accumulator of the supply device can be advantageously designed in the form of a piston accumulator.

The use of a piston accumulator opens up the advantageous possibility of mechanically preloading the piston of the piston accumulator for movement in the direction toward the oil side, for example by means of a spring arrangement. In the event of gas pressure of the pressure chamber in the cylinder chamber prevailing on the gas side of the piston accumulator, a correspondingly higher pressure level arises in the oil pressure chamber due to the mechanical preloading of the accumulator piston, whereby the sealing element sealing against the gas pressure is appropriately pressure-supported in an advantageous manner.

In especially advantageous embodiments, the piston accumulator is integrated into the end piece of the cylinder tube containing the sealing arrangement in such a way that the gas side of the accumulator cylinder is open to the pressure chamber of the cylinder tube. The gas cylinder, including the sealing arrangement supported by oil pressure and the associated supply device, thereby forms a closed assembly without external auxiliary units.

The configuration may be advantageously carried out in such a way that the accumulator cylinder is formed in the end piece by an annular space adjacent to the pressure chamber, said annular space enclosing the piston rod and containing an annular piston. With the given external dimensions of the cylinder tube and the end piece thereof, a large volume is thereby advantageously available for the piston accumulator and therefore a large oil supply for supplying the oil pressure chamber.

On the one hand, a larger volume of gas is available in the case of embodiments in which a hollow piston rod in the form of a straight length of tubing is provided, the inner end of which is open to the pressure chamber of the cylinder tube. On the other hand, with the given external dimensions and stroke lengths of the cylinder, the total gas volume in the extended position, as well as the change in volume that can be achieved by the displacement movement, can be freely adjusted by means of the dimensioning of the diameter of the piston rod (inner diameter and outer diameter) and the cylinder tube. The force-stroke characteristic of the gas cylinder can thereby be advantageously influenced.

In especially advantageous embodiments, the sliding element at the end of the piston rod has a piston-like guide component. This guide component may have gas outlets, which have a choke effect on displacement movements when outlets are selected that have a small cross section, or which have no choke effect on displacement movements in the case of a large-scale shape, so that the sliding element purely fulfills a guiding function on the inside of the cylinder tube.

The guide component may be non-circular, and may be designed in such a way that it is guided along the wall of the cylinder tube only at corner regions, wherein sliding guides may be provided at the corner regions and/or on the inner wall.

The invention is described in greater detail below based on embodiments, which are illustrated in the drawings. Shown are:

FIG. 1 a schematically simplified longitudinal section of an embodiment of the gas cylinder according to the invention;

FIG. 1A an enlarged partial representation of the region of FIG. 1, marked with a dashed-dotted line;

FIG. 2 a schematically simplified longitudinal section of a second embodiment of the gas cylinder;

FIG. 2A an enlarged partial representation of the region of FIG. 2, marked with a dashed-dotted line;

FIG. 3 a schematically simplified longitudinal section of an additional embodiment of the gas cylinder;

FIG. 3A an enlarged partial representation of the region of FIG. 3, marked with a dashed-dotted line;

FIG. 4 a schematically simplified and enlarged partial longitudinal section of an additional embodiment, showing only the end piece of the cylinder tube having the sealing arrangement;

FIG. 5 a schematically simplified longitudinal section of the gas cylinder of an additional embodiment;

FIGS. 5A and 5B an enlarged illustration of two alternative embodiments of the region of FIG. 5, marked with a dashed-dotted line;

FIG. 6 a schematically simplified longitudinal section of an additional embodiment of the gas cylinder;

FIG. 7 a cross-sectional view corresponding to the intersecting line VII-VII in FIG. 6;

FIG. 8 a schematically simplified longitudinal section of an additional embodiment of the gas cylinder according to the invention, without a sliding element;

FIG. 9 a longitudinal section of a sealing solution for a gas cylinder, in which, similar to the illustration according to FIG. 8, the annular piston rests directly on the outer circumference of the hollow cylindrical piston rod;

FIG. 10 a schematically drawn, simplified longitudinal section of an additional embodiment of the gas cylinder according to the invention, in which the sliding element of the piston rod, which is designed as a piston head, has throttle valves and non-return valves to control the fluid; and

FIG. 11 a schematic diagram of a monitoring device for the piston position of the sealing system, preferably implemented by means of an ultrasonic sensor.

The embodiment shown in FIG. 1 has a cylinder tube 1, at the closed end 3 of which a bearing eye 5 is located. At the opposite end, the cylinder tube 1 has a cylinder end piece 7, which forms a sealed duct for a piston rod 9, at the end of which a bearing eye 11 is located. The piston rod 9 is sealed against the end piece 7 by means of a sealing arrangement 13. The piston rod 9 has the form of a cylindrical hollow body, so that a tube is formed, the inner end 15 of which is open to the pressure chamber 17 of the cylinder tube 1. The pressure chamber 17 is filled with a high-pressure working gas such as N2 (via a filling connector, which is not shown). A piston-like guide component 19 is located at the open end 15 of the piston rod 9, said guide component being guided along the inner wall of the cylinder tube 1 when the piston rod 9 is moved. There are ducts 21 located in the guide component 19, which connect the pressure chamber 17 to the annular space 23 surrounding the piston rod 9 as a partial volume of the pressure chamber 17. The tube that forms the inside of the piston rod 9 is available as an additional partial volume.

As can clearly be seen in the partial section of FIG. 1A, the sealing arrangement 13 comprises several components. To this end, three annular grooves 25, 27 and 29 are formed in the end piece 7, offset from one another, which encircle the piston rod 9. A first sealing element 31 is located in the annular groove 25 nearest to the annular space 23. The subsequent annular groove 27 in the axial direction forms an oil pressure chamber 33. A second sealing element 35 is located in the annular groove 29 located furthest away from the annular space 23.

The oil pressure chamber 33 serves to accommodate high-pressure oil, which is which is pressurized to at least the same degree as the gas pressure prevailing in the cylinder tube 1. In the present case, a supply device in the form of a hydraulic accumulator 37 is provided in order to supply the oil pressure chamber 33, the oil side 39 of which hydraulic accumulator is directly connected to the oil pressure chamber 33 by means of a connection 41. The gas side 43 of the hydraulic accumulator 37 is connected to the annular space 23 of the cylinder tube 1 by means of a connection 45. The hydraulic accumulator 37 is preloaded with the gas pressure prevailing in the cylinder tube 1 thereby, so that the hydraulic accumulator 37 maintains a corresponding oil pressure in the oil pressure chamber 33. The first sealing element 31 seals the gas against the oil with the balanced pressure prevailing at the sealing element 31 thereby, while the outer, second sealing element 35 seals high-pressure oil against the environment. The sealing task is thus divided into two manageable sub-tasks, thus reducing the risk of gas loss into the environment.

It is understood that, as may also be the case in the further embodiments to be described below, the sealing arrangement 13 may have more than two axial sealing elements that are axially offset to one another, having a corresponding number of oil pressure chambers located between said sealing elements.

FIGS. 2 and 2A show an embodiment, which only differs from that shown in FIGS. 1 and 1A in that an oil connection 47 is provided for the supply device, which, secured by a non-return valve 49, makes it possible to refill sealing oil on the oil side 39 of the hydraulic accumulator 37 by means of the connection 41.

The additional embodiment shown in FIGS. 3 and 3A differs from the preceding examples in that the hydraulic accumulator of the oil-pressure supply device is formed by a piston accumulator 51, and in that this piston accumulator is integrated in the cylinder end piece 7. To this end, a bore 53 is formed in the end piece 7 functioning as an accumulator cylinder, said bore being adjacent to the annular space 23 of the cylinder tube 1. An accumulator piston 55 seals the oil side 39 of the piston accumulator 51, which side is connected to the oil pressure chamber 33, opposite the gas side 43, which is immediately adjacent to the annular space 23. A compression spring 58 clamped between a retaining ring 57 and the accumulator piston 55 preloads the accumulator piston 55 in the direction of the oil side 39, so that the oil pressure in the oil pressure chamber 33 is somewhat increased as compared to the gas pressure prevailing in the cylinder tube 1 in a manner that corresponds to the mechanical preloading. The sealing element 31 located closest to the annular space 23 is therefore pressure-supported against the gas pressure, thereby further improving the sealing behavior.

FIG. 4 shows a variant design of the piston accumulator 51. The accumulator cylinder thereof is formed by an annular space 59 thereby, which is concentric to the piston rod duct in the cylinder end piece 7 and which, as a component of the pressure chamber 17, is adjacent to the annular space 23. An annular piston 61 is disposed as an accumulator piston in the accumulator piston formed by the annular space 59. As in the preceding example, the annular piston 61 is preloaded by means of a compression spring 58, which is supported on a retaining ring 57.

The embodiments according to FIGS. 5, 5A and 5B are examples, in which the supply device for the supply of oil pressure to the oil pressure chamber 33 is provided with a monitoring device for the oil supply. In this regard, FIG. 5A shows a mechanical solution, in which the accumulator piston 55 of the piston accumulator 51 is provided with a measuring rod 63, which is guided outward by means of an oil seal 65 and indicates the position of the accumulator piston 55 and therefore the size of the oil supply in the piston accumulator 51.

By contrast, FIG. 5B shows a solution in which a pressure sensor 67 indicates the oil pressure in the oil side 39 of the piston accumulator 51. In the event that there is no oil supply on the oil side 39, the pressure indicated will be equal to zero. The zero indicator may also indicate that there is no gas pressure in the cylinder tube 1. In order to ensure that the monitoring of the oil supply is unambiguous, a second pressure sensor 69 can also monitor the gas pressure in the annular space 23, in order to compare this pressure value with the value indicated by the first pressure sensor 67.

FIGS. 6 and 7 show an additional embodiment, in which the guide component 19 located at the end 15 of the piston rod 9 is triangular in shape and is only guided on the inside of the cylinder tube 1 at the corner regions 71 of that piston rod. Sliding members 73 may be provided at the corner regions 71 of the guide component 19 for such a sliding guide, said sliding members being guided in guide grooves 75, which are incorporated into the wall of the cylinder tube 1. Alternatively, guide rails 77 may be provided on the wall of the cylinder tube 1 to guide the guide component 19 of the piston rod 9.

The following embodiments are only explained insofar as they differ from the embodiments described above. In so doing, for the most part the same reference numerals that were used above will be used for the same components, wherein in this respect, the explanations given above shall also apply to the embodiments described below.

Thus the gas cylinder solution according to FIG. 8 differs from the embodiment according to FIG. 1 in that the piston rod 9 does not have a guide component in the form of a piston head, but instead, in this embodiment the outer circumference of the free end of the piston rod 9 is guided via the ring seal 14 along the inner circumference of the cylinder tube 1 in a sealing manner. Such a ring seal 14 is disposed in the end region of the piston rod 9 at the height of the end 15 thereof.

A technical solution of this kind creates a very large accumulator space, formed by the hollow cylindrical recesses within the cylinder tube 1 and the piston rod 9. Other working media, preferably in a gaseous form, may be used instead of the nitrogen working gas, such as noble gases, in order to be able to optimally adjust the working and storage capacity of the gas cylinder to the given application situation.

The embodiment according to FIG. 9 essentially corresponds to the embodiments according to FIGS. 3 and 3A with the stipulation that the annular accumulator piston 55 is inserted into a circumferential recess 54 of the cylinder tube 1, and the outer and inner circumference of said piston are sealed, wherein an outer ring seal 56 of the accumulator piston 55 is supported on the inner circumference of the circumferential recess 54 in the form of a hollow cylindrical annular groove, and the additional sealing ring member 56′, extending along the inner circumferential side, is supported on the cylindrical outer wall of the piston rod 9.

The embodiment according to FIG. 10, on the other hand, corresponds to the illustration according to FIGS. 1 and 1A with the stipulation that valve units 78 at least partially replace the ducts 21. Such valve components 78 in the guide component 19, which forms a kind of piston head, preferably comprise an adjustable choke or gate 80, wherein a spring-loaded non-return valve 82 connected in parallel may be used here, the direction of opening of which may optionally be oriented towards the interior of the cylinder tube or the interior of the hollow cylindrical piston rod 9. In the different embodiments according to FIG. 10 shown, the gas or fluid flows between the aforementioned chambers, thus between the chamber 23 and the interior of the piston rod 9, can be controlled by means of the aforementioned throttle valve and/or non-return valve 80, 82.

In the case of the embodiment according to FIG. 11, which is essentially modeled based on the embodiments shown in FIGS. 5, 5A and 5B, an ultrasound measuring head 90 serves to determine the respective displacement position of the accumulator piston 55 within the recess of the of the cylindrical guide tube 1. Instead of the ultrasonic sensor 90, which can be electrically connected to a voltage source and/or evaluation unit, other position sensing systems (not shown) may be used for the accumulator piston 55.

As made clear by the preceding embodiments, the force-stroke characteristic of the gas cylinder can be adjusted in particular by means of the selection of the outer and inner diameter of the piston rod 9 and the inner diameter of the cylinder tube 1. 

1. A gas cylinder, in particular high-pressure gas cylinder, the cylinder tube of which (1) has a piston rod (9) that is passed through a sealing arrangement (13), which seals the gas pressure prevailing in the pressure chamber (17, 23) of the cylinder tube (1) against the ambient pressure, characterized in that the sealing arrangement (13) has a pressurized oil chamber (33) between at least one sealing element (31) adjacent to the pressure chamber (17, 23) and at least one additional sealing element (35) further away from the pressure chamber (17, 23), into which compressed oil can be compressed by means of a supply device (37, 51) at a pressure that is equal to or higher than the respective gas pressure prevailing in the pressure chamber (17, 23) of the cylinder tube (1).
 2. The gas cylinder according to claim 1, characterized in that the piston rod (9) has a movable sliding element (19) in the cylinder tube (1).
 3. The gas cylinder according to claim 1, characterized in that the sealing elements (31, 35) of the sealing arrangement (13) and the pressurized oil chamber (33) located between these sealing elements are disposed in a fixed positional relationship to one another.
 4. The gas cylinder according to claim 1, characterized in that the supply device has a hydraulic accumulator (37; 51), the oil side (39) of which, which contains sealing oil, can be connected to the pressurized oil chamber (33) and the gas side (43) of which can be connected to the pressure chamber (17, 23) of the cylinder tube (1).
 5. The gas cylinder according to claim 1, characterized in that the supply device has an oil connection (47), by means of which the sealing oil for the oil side (39) of the hydraulic accumulator (37, 51) can be refilled.
 6. The gas cylinder according to claim 1, characterized in that the supply device has a device (63; 67, 69) for monitoring the quantity of sealing oil.
 7. The gas cylinder according to claim 1, characterized in that the monitoring device has at least one pressure sensor (67, 69).
 8. The gas cylinder according to claim 1, characterized in that the hydraulic accumulator of the supply device is designed in the form of a piston accumulator (51).
 9. The gas cylinder according to claim 1, characterized in that the piston (55; 61) of the piston accumulator (51) is mechanically preloaded for movement towards the oil side (39).
 10. The gas cylinder according to claim 1, characterized in that the piston accumulator (51) in the end piece (7) of the cylinder tube (1) containing the sealing arrangement (13) is integrated in such a way that the gas side (43) of the accumulator cylinder (53; 59) is open to the pressure chamber (17, 23) of the cylinder tube (1).
 11. The gas cylinder according to claim 1, characterized in that the accumulator cylinder is formed in the end piece (7) by an annular space (59) adjacent to the pressure chamber (17, 23), said annular space enclosing the piston rod (9) and containing an annular piston (61).
 12. The gas cylinder according to claim 1, characterized in that a hollow piston rod (9) is provided in the form of a straight length of tubing, the inner end (15) of which is open to the pressure chamber (17) of the cylinder tube (1).
 13. The gas cylinder according to claim 1, characterized in that the sliding element at the end (15) of the piston rod (9) has a piston-like guide component (19).
 14. The gas cylinder according to claim 1, characterized in that the guide component (19) is formed such that it is non-circular, and is guided along the wall of the cylinder tube (1) at corner regions (71) by means of sliding guides (73; 75).
 15. The gas according to claim 1, characterized in that the force-stroke characteristic of the gas cylinder can be adjusted by means of the selection of the outer and inner diameter of the piston rod (9) and the inner diameter of the cylinder tube (1). 